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authorStephen Warren <swarren@nvidia.com>2012-09-10 17:05:01 -0600
committerStephen Warren <swarren@nvidia.com>2012-09-11 10:06:14 -0600
commitce32ddaa7087da7c9d43751db423281711a1ff2e (patch)
tree4918a9517b5e0175e2dbdf2a75b542f712d30aa7 /arch/arm/mach-tegra
parent7a74a4436b20980f8e19138e857bc7e39db5ad4b (diff)
downloadop-kernel-dev-ce32ddaa7087da7c9d43751db423281711a1ff2e.zip
op-kernel-dev-ce32ddaa7087da7c9d43751db423281711a1ff2e.tar.gz
ARM: tegra: cpu-tegra: explicitly manage re-parenting
When changing a PLL's rate, it must have no active children. The CPU clock cannot be stopped, and CPU clock's divider is not used. The old clock driver used to handle this by internally reparenting the CPU clock onto a different PLL when changing the CPU clock rate. However, the new common-clock based clock driver does not do this, and probably cannot do this due to the locking issues it would cause. To solve this, have the Tegra cpufreq driver explicitly perform the reparenting operations itself. This is probably reasonable anyway, since such reparenting is somewhat a matter of policy (e.g. which alternate clock source to use, whether to leave the CPU clock a child of the alternate clock source if it's running at the desired rate), and hence is something more appropriate for the cpufreq driver than the core clock driver anyway. Cc: Prashant Gaikwad <pgaikwad@nvidia.com> Cc: Peter De Schrijver <pdeschrijver@nvidia.com> Signed-off-by: Stephen Warren <swarren@nvidia.com>
Diffstat (limited to 'arch/arm/mach-tegra')
-rw-r--r--arch/arm/mach-tegra/cpu-tegra.c48
1 files changed, 47 insertions, 1 deletions
diff --git a/arch/arm/mach-tegra/cpu-tegra.c b/arch/arm/mach-tegra/cpu-tegra.c
index ceb52db..627bf0f 100644
--- a/arch/arm/mach-tegra/cpu-tegra.c
+++ b/arch/arm/mach-tegra/cpu-tegra.c
@@ -49,6 +49,8 @@ static struct cpufreq_frequency_table freq_table[] = {
#define NUM_CPUS 2
static struct clk *cpu_clk;
+static struct clk *pll_x_clk;
+static struct clk *pll_p_clk;
static struct clk *emc_clk;
static unsigned long target_cpu_speed[NUM_CPUS];
@@ -71,6 +73,42 @@ static unsigned int tegra_getspeed(unsigned int cpu)
return rate;
}
+static int tegra_cpu_clk_set_rate(unsigned long rate)
+{
+ int ret;
+
+ /*
+ * Take an extra reference to the main pll so it doesn't turn
+ * off when we move the cpu off of it
+ */
+ clk_prepare_enable(pll_x_clk);
+
+ ret = clk_set_parent(cpu_clk, pll_p_clk);
+ if (ret) {
+ pr_err("Failed to switch cpu to clock pll_p\n");
+ goto out;
+ }
+
+ if (rate == clk_get_rate(pll_p_clk))
+ goto out;
+
+ ret = clk_set_rate(pll_x_clk, rate);
+ if (ret) {
+ pr_err("Failed to change pll_x to %lu\n", rate);
+ goto out;
+ }
+
+ ret = clk_set_parent(cpu_clk, pll_x_clk);
+ if (ret) {
+ pr_err("Failed to switch cpu to clock pll_x\n");
+ goto out;
+ }
+
+out:
+ clk_disable_unprepare(pll_x_clk);
+ return ret;
+}
+
static int tegra_update_cpu_speed(unsigned long rate)
{
int ret = 0;
@@ -101,7 +139,7 @@ static int tegra_update_cpu_speed(unsigned long rate)
freqs.old, freqs.new);
#endif
- ret = clk_set_rate(cpu_clk, freqs.new * 1000);
+ ret = tegra_cpu_clk_set_rate(freqs.new * 1000);
if (ret) {
pr_err("cpu-tegra: Failed to set cpu frequency to %d kHz\n",
freqs.new);
@@ -183,6 +221,14 @@ static int tegra_cpu_init(struct cpufreq_policy *policy)
if (IS_ERR(cpu_clk))
return PTR_ERR(cpu_clk);
+ pll_x_clk = clk_get_sys(NULL, "pll_x");
+ if (IS_ERR(pll_x_clk))
+ return PTR_ERR(pll_x_clk);
+
+ pll_p_clk = clk_get_sys(NULL, "pll_p");
+ if (IS_ERR(pll_p_clk))
+ return PTR_ERR(pll_p_clk);
+
emc_clk = clk_get_sys("cpu", "emc");
if (IS_ERR(emc_clk)) {
clk_put(cpu_clk);
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